For many years it has been known in the art to provide facsimile transceivers which are adapted to scan a document at a first location and transmit a signal representative of dark/light variations in that document over a link such as, typically, a telephone line, and to receive such signals, demodulate them, and print out a facsimile of the document scanned by a similar transceiver at a remote location. In the prior art, such facsimile transceivers have typically printed by electrostatically "burning" a specially prepared paper to produce dark/light variations on the surface of the paper. However, such papers are expensive and additionally cause pollution in the atmosphere due to their burning of the surface of the paper and, hence, it has been a need of the art to replace such electrostatic burning printing methods with other methods, in particular other methods not requiring expensive specially treated papers.
To this end, it has been known in the art to provide an ink jet printer apparatus according to which a stream of ink droplets are emitted from an orifice in response to the received signals. Several different types of ink jet apparatus have been proposed. Chief among these are ones in which a continuous stream of drops is emitted from the orifice of the ink jet, those droplets not required for printing being electrostatically deflected and typically recycled for re-emission. Another type of ink jet apparatus is the "impulse" type, in which the ink droplets are emitted only in response to print commands. The present invention has applicability to both types, but in a preferred embodiment relates to the impulse type of jet.
It will be appreciated by those skilled in the art that the typical document to be transmitted by a facsimile transceiver is a typed or otherwise printed document which typically comprises only about 5% to 10% printing, the remainder being white paper. Therefore, if a continuous stream type of ink jet printer is to be used, in order to provide efficient use of ink, all the ink not required for printing must be efficiently caught, after having been deflected, and recycled. This recycling typically involves elaborate filtering, bubble elimination and cleansing and pressurizing schemes. For this reason, at least, it would be desirable to use the "impulse" printing system in which ink droplets are emitted only in response to print commands. Thus the ink recycle and associated filtering and bubble elimination apparatus can be eliminated simplifying the assembly immensely. However, to date there has not been provided in the art a workable impulse ink jet system.
It will also be appreciated by those skilled in the art that if a facsimile apparatus is to be useful in the typical office environment in which skilled personnel are not available to maintain and repair the ink jet apparatus, it must be relatively foolproof. To this end, copending application Ser. No. 203,583, has been filed on Nov. 3, 1980 in the name of K. W. Bower. This invention relates to disposable ink jet printing apparatus comprising the ink jet itself, a reservoir of ink and pump means for supplying the ink to the ink jet for purposes of priming and purging the jet prior to printing, capillary action supplying the ink to the jet thereafter. The invention of Bower comprises the idea that this ink jet apparatus can be made in a unitary assembled way and be manufactured sufficiently inexpensively that the entire assembly can be made disposable, thus eliminating the need for skilled personnel to be available in the environment in which the ink jet facsimile apparatus is to be used. Therefore, if anything goes amiss with the ink jet printer, or if the ink should be consumed, the entire assembly can be readily removed and disposed of and replaced by essentially unskilled personnel. This offers the additional advantage that the ink jet may be connected to the reservoir at the point of manufacture therefore eliminating the necessity of elaborate connection means which has occupied numerous inventors in the prior art. The invention of Bower also includes the broad concept of dividing various pump functions among disposable and nondisposable parts of the apparatus, thus lowering the cost of the disposable portions.
A second related application is that assigned Ser. No. 203,584, filed Nov. 3, 1980, in the name of W. Salmre. In that application, it is disclosed that the pumps of the Bower invention can most advantageously be made by using the "peristaltic" pumping principle in which a resilient tube is progressively compressed along its axial direction so that a pressure differential is produced across its ends. This inexpensive valveless pumping apparatus can be used to supply ink to the jet for priming and purging purposes. The present invention relates to a practical commercial preferred embodiment of both the Bower and Salmre inventions. That is, it comprises peristaltic pumping means for use in conjunction with disposable ink jets and reservoirs of ink for use, in particular, in facsimile apparatus, though applicable to other forms of ink jet printing machinery.